The proposed project is an attempt to achieve a better understanding of neural and biochemical bases of biological rhythms, specifically those with periods of approximately 24 hours (circadian rhythms). The suprachiasmatic nuclei and other hypothalamic structures will be exposed to drugs which inhibit protein synthesis and the effects of these manipulations on circadian rhythms in eating, drinking, and locomotor activity of rats will be assessed. Drugs which interfere with common neurotransmitters will also be used to investigate the role these transmitters play in the generation and entrainment of rhythmic functions. In these experiments, the animals will be exposed to a light-dark cycle, constant light, and to phase shifts in the light-dark cycle.